Traffic signals have long been used to regulate the flow of traffic at intersections. Generally, traffic signals have relied on timers or vehicle sensors to determine when to change the phase of traffic signal lights, thereby signaling alternating directions of traffic to stop, and others to proceed.
Emergency vehicles, such as police cars, fire trucks and ambulances, are generally permitted to cross an intersection against a traffic signal. Emergency vehicles have typically depended on horns, sirens and flashing lights to alert other drivers approaching the intersection that an emergency vehicle intends to cross the intersection. However, due to hearing impairment, air conditioning, audio systems and other distractions, often the driver of a vehicle approaching an intersection will not be aware of a warning being emitted by an approaching emergency vehicle.
There are presently a number of known optical vehicle priority systems that have equipment installed at certain traffic signals and on emergency vehicles. An optical signal from an optical emitter mounted to an emergency vehicle can transmit light pulses encoding a priority preemption request. The equipment installed at a traffic signal can adjust the phase of the traffic signal to expedite passage through the traffic signal by the emergency vehicle.
In these known optical vehicle priority systems, the operators of the emergency vehicle manually activate the optical emitter. This approach can be disadvantageous for certain applications or environments. For example, an operator can forget to activate the optical emitter when rushing to respond to an emergency situation. In addition, an operator can abuse the optical vehicle priority system by activating the optical emitter while not responding to an emergency situation. Abuse of an optical vehicle priority system can needlessly disrupt the normal traffic flow through the affected intersections.